Five-Year Outcome of Children With “Growing Pains”: Correlations With Pain Threshold
Article Outline
Objective
To examine the 5-year outcome in a cohort of children with “growing pains” and the association with changes in pain threshold.
Study design
Subjects were 44 children with growing pains studied previously, and controls were 38 pain-free children matched by sex and age. Current status of growing pains and other pain syndromes were assessed by parental questionnaires. Pain threshold was measured with a Fisher-type dolorimeter. Outcomes were correlated with the pain threshold.
Results
We examined 35/44 patients (80%) after 5 years. Eighteen patients (51%) experienced resolution of growing pains. In 14 of the 17 patients with persistent growing pains (83%), episodes were less frequent and milder. The prevalence of accompanying pain syndromes decreased from 20% to 14%. No patient developed fibromyalgia. Pain thresholds were similar in the entire growing pains cohort and healthy controls, but those with continued growing pains had significantly lower thresholds than controls (P <.05) and patients with resolved growing pains (P <.02).
Conclusions
We confirm that growing pains has a benign prognosis and probably represents a pain amplification syndrome of early childhood.
The most common cause of recurrent childhood musculoskeletal pain, termed “growing pains,” affects between 3% and 37% of children,1, 2 primarily those age 3-12 years. In a previous study we showed that patients with growing pains have lower pain thresholds than their peers,3 suggesting that growing pains represents a noninflammatory pain amplification syndrome in early childhood. Several studies also have found increased prevalence of other pain syndromes, including abdominal pain and headaches, in children with growing pains.4, 5
Growing pains is widely considered a benign syndrome, with resolution occurring in the vast majority of children by late childhood.6 Very few studies have actually investigated whether this assumption is true by studying the outcome of growing pains in well-defined cohorts.2 It is important to determine whether patients with growing pains develop other pain syndromes in adolescence, such as fibromyalgia, characterized by a low pain threshold and often marked lifelong morbidity.7, 8, 9
In this study, we investigated the 5-year outcome of the cohort that we studied previously, including the development of other pain syndromes, and explored whether the factors that we found to be associated with growing pains are associated with outcome in these patients.
Methods
Our original cohort included 44 children with growing pains recruited from pediatric rheumatology clinics and participating child community health centers. The initial diagnosis of growing pains was confirmed by a pediatric rheumatologist based on the typical clinical characteristics outlined by us in previous work2 and after other causes of the pain were excluded. We were able to locate and obtain consent from 35 of these children (80%) for the present study. Four children were lost to follow-up, 3 refused to provide consent, and 2 did not appear for evaluation. There were no significant demographic and clinical differences between the patients from the first study lost to follow-up and the patients included in the current study.
The control group comprised 38 healthy age, sex-matched children with no history of growing pains from our clinics. The study was approved by the institutional human rights board.
Demographic data collected included age, sex, and ethnicity. The clinical characteristics of growing pains, including duration, frequency of attacks, location of pain, sleep quality (parental and self-report questions on the general quality of sleep), days of school missed, development of other pain syndromes, and the use of various analgesic measures (including complementary medicine), were recorded.
Pain thresholds were assessed in predefined body areas using a Fisher-type dolorimeter (model PTH pressure threshold meter, 10 kg range, 1/10 kg; PDT, Great Neck, New York). The same physician (Y.U.) measured pain thresholds in all patients by gradually increasing the pressure in increments of 1 kg/second until the patient reported feeling pain. The pain threshold was measured in 18 predefined pressure points of fibromyalgia, 3 control points (distal right arm, forehead, and left thumb), and in the mid-anterior tibia below the tibial tuberosity in both legs, where patients usually report pain during episodes of growing pains.
The unpaired Student t test and the χ2 test were used to compare data in patients and controls, as appropriate for tender points. Pearson correlations were performed to evaluate the relationship between pain thresholds and clinical characteristics of growing pains.
Results
The 35 patients in this cohort included 20 males (57%) and 15 females (43%) with a mean age of 13.4 ± 2.7 years. Twenty-three children were Jewish, and 12 were Arab Moslems. Follow-up was 5 years after the original study. The 38 controls included 20 males (53%) and 18 females (47%), with a mean age of 13.6 ± 2.7 years. Two of the controls had a past history of headaches, and 1 control had recurrent abdominal pain, but none had active pain during the year before the study.
Seventeen patients (49%) reported persistent growing pains. The pains worsened in only 3 of these patients (18%); in the other 14, the frequency of pain episodes was significantly decreased (P <.001) (Table I). Continued pain episodes were significantly more prevalent in children with a family history of at least one parent with a pain syndrome than in those without a family history (P = .047). Sixteen children (94%) complained of pain in the lower extremities, and 5 (28%) had pain in the upper extremities. The pain was symmetric in 15 children (88%). Nine children (53%) used analgesics. Five children (14%) reported symptoms of other pain syndromes, including 3 (9%) with migraine-like headaches and 2 (5%) with recurrent abdominal pain. In our previous study, the prevalence of other pain syndromes was 20%. No patient developed fibromyalgia. Thirty-two patients reported good sleep quality and 2 reported moderate sleep quality; none reported poor sleep. Nine patients (53%) used analgesics to relieve pain; none used complementary medicine techniques. No school absences related to pain episodes were reported. There was no correlation of the outcome with sex, ethnicity, or age. No patient developed arthritis.
Table I. Frequency of growing pains episodes
| Frequency | First study, n (%) | Second study, n (%) |
|---|---|---|
| No episodes | 0 (0) | 18 (51) |
| <1 per month | 17 (39) | 8 (24) |
| ≥1 per month <1 per week | 8 (18) | 4 (11) |
| ≥1 per week | 19 (43) | 5 (14) |
Pain Threshold
There were no differences in pain threshold between the growing pains and control groups at any pressure point measured (Table II). However, the pain thresholds were significantly lower in the 17 patients with persistent growing pains compared with the control group and also with those patients whose growing pains resolved in fibromyalgia and anterior tibia pressure points, but not in control pressure points (Table II).
Table II. Pressure applied by dolorimeter to cause pain (mean ± SD, kg/cm2)
| Pressure point | Total growing pains (n = 35) | Resolved growing pains (n = 18) | Continued growing pains (n = 17) | Controls (n = 38) |
|---|---|---|---|---|
| Fibromyalgia points | 4.7 ± 1.1 | 5.1 ± 1.3∗ | 4.2 ± 0.7† | 4.9 ± 1.1 |
| Control points | 4.7 ± 1.3 | 5.1 ± 1.5 | 4.2 ± 1.0 | 4.7 ± 1.1 |
| Anterior tibia | 6.0 ± 1.5 | 6.5 ± 1.8‡ | 5.4 ± 1.1† | 6.2 ± 1.4 |
∗P <.02 compared with continued growing pains. |
†P <.05 compared with control. |
‡P <.05 compared with continued growing pains. |
At least one tender point at a pressure of <5 kg/cm2 was detected in 82% of the children with persistent growing pains versus 58% of controls and 44% of those with resolved growing pains (P <.01). At least one tender point at a pressure of <4 kg/cm2 was found in 41% of the children with persistent growing pains versus 21% of controls and 22% of those with resolved growing pains (P <.01). In the anterior tibia region, reported as painful in nearly all patients with persistent growing pains, 41% of the patients with persistent growing pains reported pain at a pressure level of <5 kg/cm2, compared with 21% of controls and 11% of those with resolved growing pains (P <.01) (Figure).
Figure.
Proportion of patients reporting pain at a pressure of <5 kg/cm2 applied by a dolorimeter.
Discussion
Growing pains is considered a self-limiting phenomenon. In the present study, we found that growing pains resolved after 5 years in slightly more than 50% of the patients and improved in nearly all of the others, with less-frequent episodes, less use of analgesics, and fewer school absences related to pain. The lack of resolution of typical growing pains in a large proportion of our cohort in adolescence was somewhat surprising, however, and is a novel finding. We found that the patients without resolution had a higher prevalence of a parent with a pain syndrome. There was also a decrease in the prevalence of headaches and abdominal pain from our previous study, and no patient developed symptoms and signs compatible with fibromyalgia; however, with only 35 patients, the power of this study to detect cases of fibromyalgia is low. Assuming a 1%, 3%, and 6% prevalence of fibromyalgia,8, 9 the probability of detecting one case of fibromyalgia in our cohort would be only 30%, 66%, and 89%, respectively.
This decrease in growing pains symptoms seemed to correlate with an increased pain threshold in the patients in whom growing pains resolved to levels equal with those of controls. Patients with persistent growing pains still had lower pain thresholds, not only in the anterior tibia but also at typical fibromyalgia points, indicating that growing pains is a pain amplification syndrome. We did not investigate the potential causes of the increased pain thresholds over these 5 years. We found no evidence supporting sleep difficulties as an explanation for the low pain threshold in the patients with persistent growing pains.
Our findings lend support to our hypothesis that growing pains represents a pain amplification syndrome with a general improvement over time in the vast majority of patients but with incomplete resolution in nearly 50%. The major shortcoming of the present study is the small size of our cohort to detect fairly rare events like fibromyalgia. Other limitations are related to the lack of data collected during follow-up on factors that could affect musculoskeletal pain, such as diet, physical activity, vitamin D metabolism, and detailed sleep and psychosocial information. It will be important to follow the course of pain syndrome in our cohort again in early adulthood.
References
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- . Decreased pain threshold in children with growing pains. J Rheumatol. 2004;31:610–613
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- . Recurrent abdominal pain, headache and limb pains in children and adolescents. Pediatrics. 1972;50:429–436
- . “Growing pains” in childhood: a proposal for treatment. J Pediatr Orthop. 1988;8:402–406
- . Fibromyalgia syndrome in children: an outcome study. J Rheumatol. 1995;22:525–528
- Assessment of nonarticular tenderness and prevalence of fibromyalgia in children. J Rheumatol. 1993;20:368–370
- . Fibromyalgia syndrome in children and adolescents: clinical features at presentation and status at follow-up. Pediatrics. 1998;101:377–382
The authors declare no conflict of interest.
PII: S0022-3476(09)01213-X
doi:10.1016/j.jpeds.2009.11.078
© 2010 Mosby, Inc. All rights reserved.
